River Machno (Welsh: Afon Machno) is a river in Snowdonia in north-west Wales. It is the first major tributary of the River Conwy, which it joins south of Betws-y-coed, past the Pandy Falls and the Machno Falls.

It has its source in the slopes at the head of the Machno valley, and flows through the villages of Cwm Penmachno and Penmachno.

The Snowdonia Slate Trail follows the whole length of the Machno Valley.

53°04′N 3°47′W / 53.067°N 3.783°W / 53.067; -3.783